Proposed work is a continuation of our studies on renal and intestinal transport mechanism of amino acids, sugars and electrolytes. Recently we have investigated the effect of 3 diuretics, ethacrynic acid (EA), furosemide and amiloride, on intestinal transport of electrolytes and found that they not only inhibit the net Na absorption but also the net C1 secretion. The differences in the effect of these diuretics are: EA inhibits the transmucosal transport of glucose and amino acid and has little inhibitory effect on Na and C1 in glucose-free medium while the other 2 diuretics have no inhibitory effect on glucose and amino acid transport but inhibit the electrolyte transport even in glucose-free medium. We propose to pursue this work by: (1) measuring the intra-epithelial PD (Vmc, Vcs) and resistance in presence of glucose, amino acid and the diuretics, and determining whether or not the diuretics cause a hyperpolarization of mucosal-to-cell PD; (2) studying the intra-epithelial PD of proximal tubules of the kidney during the perfusion of diuretics. Our laboratory is also engaged in the study of age changes of the renal and intestinal transport mechanism. We intend to continue this work and to determine whether there is a correlation between structural and functional changes in the absorption and elimination mechanism of aged animals. BIBLIOGRAPHIC REFERENCES: Huang, K.C. and T.S.T. Chen: Comparative biological aspects of intestinal absorption. Intestinal Absorption and Malabsorption ed. by T.Z. Csaky. Raven Press, N.Y. pp. 187-196, 1975. Chen, T.S.T., M. Ando, S. Utida and K.C. Huang: Ion fluxes and permeabilities studies of Japanese cultured eel intestine. Fed. Proc. 34: 470, 1975.